U.S. patent number 4,496,687 [Application Number 06/574,669] was granted by the patent office on 1985-01-29 for aqueous emulsion-type silicone compositions.
This patent grant is currently assigned to Shin-Etsu Chemical Co., Ltd.. Invention is credited to Morizo Nakazato, Toshio Oba, Fumio Okada.
United States Patent |
4,496,687 |
Okada , et al. |
January 29, 1985 |
Aqueous emulsion-type silicone compositions
Abstract
The invention provides a novel organopolysiloxane-containing
aqueous emulsion composition which, upon removal of water by drying
at room temperature, can give a cured rubbery elastomer having
excellent mechanical properties and exhibiting strong adhesion to
the substrate on which it has been cured. The inventive composition
is prepared by blending (A) an aqueous emulsion of an
organopolysiloxane having silicon-bonded hydroxy groups and
emulsified in water by use of an anionic surface active agent, (B)
a mixture of a reaction product of a carboxylic acid anhydride with
an amino-functional organosilane and a colloidal silica in the form
of an aqueous suspension and (C) a curing catalyst in limited
proportions.
Inventors: |
Okada; Fumio (Gunma,
JP), Oba; Toshio (Gunma, JP), Nakazato;
Morizo (Gunma, JP) |
Assignee: |
Shin-Etsu Chemical Co., Ltd.
(Tokyo, JP)
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Family
ID: |
16252625 |
Appl.
No.: |
06/574,669 |
Filed: |
January 27, 1984 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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444206 |
Nov 24, 1982 |
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Foreign Application Priority Data
|
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Nov 27, 1981 [JP] |
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56-190115 |
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Current U.S.
Class: |
524/859; 524/130;
524/131; 524/132; 524/156; 524/158; 524/195; 524/394; 524/398;
524/399; 524/588; 524/710; 524/745; 524/789; 524/837; 524/838;
524/860; 528/901 |
Current CPC
Class: |
C08J
3/03 (20130101); C08K 13/02 (20130101); C08K
5/09 (20130101); C08K 3/36 (20130101); C08K
5/54 (20130101); C08K 13/02 (20130101); C08L
83/04 (20130101); C08L 83/04 (20130101); C08K
5/54 (20130101); C08L 83/04 (20130101); C08G
77/16 (20130101); C08J 2383/04 (20130101); Y10S
528/901 (20130101); C08L 2666/44 (20130101); C08L
2666/54 (20130101) |
Current International
Class: |
C08K
13/00 (20060101); C08K 13/02 (20060101); C08J
3/02 (20060101); C08J 3/03 (20060101); C08L
83/00 (20060101); C08L 83/04 (20060101); C08L
083/02 () |
Field of
Search: |
;524/130,131,132,156,158,195,394,398,399,588,710,745,789,837,838,859,860
;528/901 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Marquis; Melvyn I.
Attorney, Agent or Firm: Toren, McGeady and Stanger
Parent Case Text
BACKGROUND OF THE INVENTION
This is a continuation-in-part application from the copending U.S.
patent application Ser. No. 444,206 filed Nov. 24th, 1982 and now
abandoned.
Claims
What is claimed is:
1. An organopolysiloxane-containing aqueous emulsion composition
which comprises
(A) an aqueous organopolysiloxane emulsion comprising
(A-1) 100 parts by weight of an organopolysiloxane having at least
two hydroxy groups directly bonded to the silicon atoms in a
molecule,
(A-2) from 0.3 to 20 parts by weight of an anionic surface active
agent, and
(A-3) water as the dispersing medium of the components (A-1) and
(A-2),
(B) from 1 to 60 parts by weight as solid of a uniform dispersion
comprising
(B-1) from 0.1 to 20% by weight, based on the component (B-2)
mentioned below as solid, of a reaction product of a carboxylic
acid anhydride with an organosilane having a functional amino group
in a molecule or a hydrolysis product thereof, and
(B-2) a colloidal silica in an aqueous suspension,
(C) a catalytic amount of a curing catalyst.
2. The organopolysiloxane-containing aqueous emulsion composition
as claimed in claim 1 wherein the organopolysiloxane has a
molecular weight of at least 10,000.
3. The organopolysiloxane-containing aqueous emulsion composition
as claimed in claim 1 wherein the anionic surface active agents is
selected from the class consisting of esters of sulfonic acid,
sulfuric acid and phosphoric acid and salts thereof.
4. The organopolysiloxane-containing aqueous emulsion composition
as claimed in claim 1 wherein the amount of the anionic surface
active agent is in the range from 0.5 to 5 parts by weight per 100
parts by weight of the organopolysiloxane.
5. The organopolysiloxane-containing aqueous emulsion composition
as claimed in claim 1 wherein the amount of water in the component
(A) is in the range from 25 to 600 parts by weight per 100 parts by
weight of the organopolysiloxane.
6. The organopolysiloxane-containing aqueous emulsion composition
as claimed in claim 1 wherein the oraganosilane having a functional
amino group is represented by the general formula R.sup.2
Si(CH.sub.3).sub.n-1 (OR.sup.1).sub.4-n, in which R.sup.1 is a
monovalent group selected from the class consisting of alkyl and
acyl groups, R.sup.2 is a monovalent group selected from the class
consisting of 2-aminoethyl, 3-aminopropyl and
N-(2-aminoethyl)-3-aminopropyl groups and n is a positive integer
of 1 or 2.
7. The organopolysiloxane-containing aqueous emulsion composition
as claimed in claim 1 wherein the carboxylic acid anhydride is
selected from the class consisting of the anhydrides of methyl
tetrahydrophthalic acid, benzophenone tetracarboxylic acid,
phthalic acid, maleic acid, pyromellitic acid, succinic acid,
trimellitic acid, phenyl maleic acid, methyl hexahydrophthalic
acid, hexahydrophthalic acid, dodecyl succinic acid, dichloromaleic
acid and chlorendic acid, ethyleneglycol bistrimellitate and
polyazelaic polyanhydride.
8. The organopolysiloxane-containing aqueous emulsion composition
as claimed in claim 1 wherein the amount of the component (B) is in
the range from 3 to 30 parts by weight as solid per 100 parts by
weight of the organopolysiloxane.
9. The organopolysiloxane-containing aqueous emulsion composition
as claimed in claim 1 wherein the curing catalyst is selected from
the class consisting of organotin compounds, metal salts of organic
acids, amine compounds and hydrochlorides thereof.
10. The organopolysiloxane-containing aqueous emulsion composition
as claimed in claim 1 wherein the amount of the curing catalyst is
in the range from 0.01 to 10 parts by weight per 100 parts by
weight of the organopolysiloxane.
11. The organopolysiloxane-containing aqueous emulsion composition
as claimed in claim 1 which has a value of pH in the range from 3
to 12.
12. A method for the preparation of an organopolysiloxanecontaining
aqueous emulsion composition comprising
(A) an aqueous organopolysiloxane emulsion comprising
(A-1) 100 parts by weight of an organopolysiloxane having at least
two hydroxy groups directly bonded to the silicon atoms in a
molecule,
(A-2) from 0.3 to 20 parts by weight of an anionic surface active
agent, and
(A-3) water as the dispersing medium of the components (A-1) and
(A-2),
(B) from 1 to 60 parts by weight as solid of a uniform dispersion
comprising
(B-1) from 0.1 to 20% by weight, based on the component (B-2)
mentioned below as solid, of a reaction product of a carboxylic
acid anhydride with an organosilane having a functional amino group
in a molecule or a hydrolysis product thereof, and
(B-2) a colloidal silica in an aqueous suspension, and
(C) a catalytic amount of a curing catalyst, which comprises the
steps of:
(a) dispersing the colloidal silica as the component (B-2) and the
reaction product as the component (B-1) in water to form a uniform
aqueous dispersion; and
(b) admixing the above prepared uniform aqueous dispersion with an
aqueous emulsion of the organopolysiloxane emulsified in water by
the aid of the anionic surface active agent and the curing
catalyst.
Description
The present invention relates to an aqueous emulsion-type silicone
composition or, more particularly, to an aqueous emulsion-type
silicone-containing composition which is very stable and storable
over a long period of time in a wide range of the values of pH of
the composition and is capable of being cured and converted even at
room temperature into a rubbery elastomer having excellent rubbery
properties upon removal of water to exhibit good adhesive bonding
to the surface of various kinds of substrate materials on which it
is dried and cured.
Various types of compositions are known in the prior art as an
aqueous emulsion-type silicone composition capable of being cured
and converted into a silicone elastomer by drying. These known
compositions are characteristic in their performance forming an
elastomer upon removal of the water contained therein and such a
characteristic performance of the composition is utilized in their
application as a coating material. Notwithstanding the importance
of the adhesive bonding to the substrate surface in a coating
material, conventional aqueous emulsion-type silicone compositions
are not always satisfactory in this respect of adhesive
bonding.
For example, the specification of Japanese Patent Kokai No.
56-16553 discloses a silicone emulsion composition having a value
of pH in the range from 9 to 11.5 and comprising an
organopolysiloxane having silicon-bonded hydroxy groups and
emulsified with stability by use of an anionic surface active
agent, a colloidal silica and an organic tin compound or an organic
amine compound. Compositions of this type have several problems
when the alkalinity exhibited by the aqueous emulsion per se is
high and in the relatively poor adhesive bonding of the silicone
elastomer formed therefrom on to the surface of various kinds of
substrate materials.
In recent years, on the other hand, various attempts have been
undertaken with an object to improve the adhesive bonding of the
aqueous emulsion-type silicone composition of the above described
type. For example, the specification of Japanese Patent Kokai No.
54-131661 discloses an organopolysiloxane latex composition which
is obtained, for example, by the emulsion polymerization of a
cyclic organopolysiloxane and a functional group-containing
organotrialkoxysilane such as an aminoalkyl trialkoxysilane and the
like in the presence of a surface active agent of the types of
sulfonates or a cationic surface active agent such as quaternary
ammonium salts, which latter class is preferred when an
amino-functional organosilane is used in combination. Furthermore,
another type of organopolysiloxane latex composition is disclosed
in the specification of U.S. Pat. No. 3,817,894 which is composed
of a block-wise organopolysiloxane copolymer formed of
dimethylsiloxane units and monophenylsiloxane units, water, a
cationic surface active agent, a non-ionic surface active agent, a
filler and an amino-functional alkoxysilane.
These organopolysiloxane latex compositions are, however, not free
from the disadvantages of poor storability because most of them
contain a cationic surface active agent as an essential component
thereof in comparison with those prepared by use of an anionic
surface active agent. As is known, the surface active agents used
in the preparation of the organopolysiloxane latex compositions are
mostly anionic since cationic surface active agents are less
preferred (see, for example, Japanese Patent Publication No.
43-18800) in respect of the storability of the composition while
serious drawbacks are sometimes unavoidable in the use of an
anionic surface active agent that the latex composition exhibits
unduly large increase in the viscosity or a phenomenon of gelation,
i.e. formation of an insoluble matter or precipitates, when the
latex composition is admixed with an amino-functional silane or a
partial hydrolysis-condensation product thereof with an object to
improve the strength of adhesion of the stabilized
organopolysiloxane latex composition.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a
novel and improved aqueous emulsion type composition containing an
organopolysiloxane, which is capable of being cured and converted
into a rubbery elastomer upon removal of the water even at room
temperature and freed from the above described problems in the
prior art compositions of the similar types due to the incompatible
requirements for the increased storability or stability and
improved performance of adhesion when the latex composition is
admixed with an organosilane having a functional amino group or a
partial hydrolysis product thereof.
Thus, the organopolysiloxane-containing aqueous emulsion-type
composition of the invention comprises:
(A) an aqueous organopolysiloxane emulsion comprising
(A-1) 100 parts by weight of an organopolysiloxane having at least
two hydroxy groups directly bonded to the silicon atoms in a
molecule,
(A-2) from 0.3 to 20 parts by weight of an anionic surface active
agent, and
(A-3) water as the dispersant of the components (A-1) and
(A-2),
(B) from 1 to 60 parts by weight as solid of a uniform dispersion
comprising
(B-1) from 0.1 to 20% by weight, based on the component (B-2)
mentioned below as solid, of a reaction product of a carboxylic
acid anhydride with an organosilane having a functional amino group
in a molecule or a hydrolysis product thereof, and
(B-2) a colloidal silica in the form of an aqueous suspension,
and
(C) a catalytic amount of a curing catalyst.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The above described organopolysiloxane-containing aqueous emulsion
composition of the present invention is very stable and storable
over a long period of time and capable of being converted and cured
upon removal of the water content into a rubbery elastomer having
excellent elastomeric properties and exhibiting good adhesion to
the surface of the substrate on which it is dried and cured. The
storability and curing performance of the inventive emulsion
composition as well as the elastomeric properties and adhesion of
the cured product thereof are not affected by the value of pH of
the emulsion composition which may range widely from 3 to 12.
Furthermore, the inventive emulsion composition can be formulated
to have such a consistency that a single coating with the
composition can give a cured rubbery layer of the composition
having a thickness as large as 5 mm or larger without cracks or
other defects.
In the following, the organopolysiloxane-containing aqueous
emulsion-type composition of the present invention is described in
further detail beginning with the description of each of the
essential components of the composition.
In the first place, the component (A) of the composition is an
aqueous emulsion of an organopolysiloxane emulsified in water by
use of a surface active agent which is preferably anionic. The
organopolysiloxane to be emulsified in water should have at least
two hydroxy groups directly bonded to the silicon atoms in a
molecule. Otherwise, the organopolysiloxane is not particularly
limitative in respect of the position of the silicon-bonded hydroxy
groups, types of the organic groups bonded to the silicon atoms,
molecular configuration, degree of polymerization and the like
parameters so that various kinds of conventional hydroxy-containing
organopolysiloxanes are suitable for use in the inventive
composition. In particular, it is preferable that the
organopolysiloxane has a molecular weight of at least 10,000 though
not limitative.
Such an organopolysiloxane can be prepared, for example, (1) by the
method in which a cyclic organopolysiloxane such as an
octaorganocyclotetrasiloxane, e.g. octamethyl cyclotetrasiloxane,
is subjected to the ring-opening polymerization reaction, (2) by
the method in which a linear-chain or branched-chain
organopolysiloxane having at least two hydrolyzable groups such as
alkoxy groups, acyloxy groups and the like in a molecule is
subjected to a hydrolysis reaction and (3) by the method in which
an organohalogenosilane or a mixture of two kinds or more of
organohalogenosilanes is subjected to a hydrolysis reaction.
The anionic surface active agents suitable for use in the
preparation of the component (A) by emulsifying the above described
organopolysiloxane in water include various kinds of conventional
ones. In particular, the anionic surface active agent should
exhibit a catalytic activity for the emulsion polymerization of the
organopolysiloxane such as the sulfonate esters, sulfate esters and
phosphate esters having surface activity as well as salts thereof
including salts of alkyl sulfates such as sodium lauryl sulfate and
the like, alkyl-substituted benzene sulfonic acid such as dodecyl
benzene sulfonic acid and the like, alkyl-substituted naphthalene
sulfonic acids, salts of polyethylene glycol sulfuric esters, salts
of lauryl phosphate and the like as the examples.
The aqueous emulsion of the organopolysiloxane may be prepared in a
variety of conventional methods. For example, an aqueous emulsion
is readily formed when the organopolysiloxane having at least two
silicon-bonded hydroxy groups in a molecule is dispersed directly
in water in the presence of an anionic surface active agent.
Alternatively, a cyclic organopolysiloxane such as octamethyl
cyclotetrasiloxane is first dispersed and emulsified in water in
the presence of an anionic surface active agent followed by the
ring-opening polymerization under heating with addition of a known
catalyst for the reaction to form an organopolysiloxane having at
least two silicon-bonded hydroxy groups in a molecule in an
emulsified state. It is optional in this in situ formation of the
organopolysiloxane as emulsified that the cyclic organopolysiloxane
is emulsified with admixture of a trifunctional organosilane
represented by the general formula RSi(OR.sup.1).sub.3, in which R
is a monovalent hydrocarbon group such as alkyl, alkenyl and aryl
groups and R.sup.1 is an alkyl group or an acyl group, or the
ring-opening polymerization of the emulsified cyclic
organopolysiloxane is performed with admixture of a separately
prepared aqueous emulsion of the above mentioned trifunctional
organosilane compound.
The amount of the anionic surface active agent used in the
preparation of the component (A), i.e. the aqueous emulsion of the
organopolysiloxane, is usually in the range from 0.3 to 20 parts by
weight or, preferably, from 0.5 to 5 parts by weight per 100 parts
by weight of the organopolysiloxane. When the amount of the anionic
surface active agent is smaller than above, no sufficient effect of
emulsification can be obtained to give a desired aqueous emulsion
of the organopolysiloxane while an excessively large amount of the
anionic surface active agent is detrimental on the rubbery
properties, e.g. tensile strength, ultimate elongation and
hardness, of the cured product obtained by drying the inventive
composition.
The amount of water in the component (A) is of course not
limitative insofar as a stable aqueous emulsion can be prepared
with the organopolysiloxane in the presence of the anionic surface
active agent. Water is used usually in an amount of 25 to 600 parts
by weight per 100 parts by weight of the organopolysiloxane.
It is optional that the aqueous emulsion of the organopolysiloxane
as the component (A) is prepared by use of a non-ionic surface
active agent such as a polyoxyethylene alkyl ether, polyoxyethylene
alkyl phenyl ether and the like as well as a fluorine-containing
surface active agent belonging to the class of an anionic,
non-ionic or amphoteric surface active agent in combination with
the above mentioned anionic surface active agent provided that the
rubbery properties of the cured product obtained by drying the
inventive composition is not adversely affected.
In the next place, the component (B) is admixed in the inventive
composition with an object to improve the adhesion of the cured
product obtained by drying the inventive composition to the surface
of the substrate on which the aqueous composition is dried. The
component (B) is also effective in preventing formation of cracks
in the cured rubbery layer of the dried composition having a
relatively large thickness.
One of the essential constituents in this component (B) is a
reaction product of a carboxylic acid anhydride and an organosilane
having a functional amino group in a molecule or a hydrolysis
product thereof. The amino-functional organosilane above mentioned
is an organosilane represented by the general formula R.sup.2
Si(CH.sub.3).sub.n-1 (OR.sup.1).sub.4-n, in which R.sup.1 has the
same meaning as defined above, R.sup.2 is an amino-substituted
alkyl group such as 3-aminopropyl, N-(2-aminoethyl)-3-aminopropyl
and the like groups and n is a positive integer of 1 or 2.
Particular examples of such amino-functional organosilane compounds
suitable in the invention include 3-aminopropyl triethoxy silane,
N-(2-aminoethyl)-3-aminopropyl methyl dimethoxy silane,
3-aminopropyl methyl diethoxy silane,
N-(2-aminoethyl)-3-aminopropyl trimethoxy silane and the like. In
the present invention, substantially the same results can be
obtained by the use of a product obtained by at least partially
hydrolyzing the above named amino-functional organosilane compound
in place of the silane compound per se.
The carboxylic acid anhydride to be reacted with the above
described amino-functional organosilane compound or a hydrolysis
product thereof is exemplified by the anhydrides of various kinds
of carboxylic acids such as methyl tetrahydrophthalic acid,
benzophenone tetracarboxylic acid, phthalic acid, ethyleneglycol
bistrimellitate, maleic acid, pyromellitic acid, succinic acid,
trimellitic acid, phenyl maleic acid, methyl hexahydrophthalic
acid, hexahydrophthalic acid, dodecyl succinic acid, dichloromaleic
acid and chlorendic acid as well as polyanhydrides such as
polyazelaic polyanhydride and the like.
The reaction between the amino-functional organosilane compound and
the above named carboxylic acid anhydride can readily proceed even
at room temperature exothermically by merely blending the reactants
together to give the desired reaction product. Although not
particularly limitative, it is preferable that the reaction of
these reactants is undertaken by diluting the reaction mixture with
a suitable organic solvent or a combination of organic solvents
such as methyl alcohol, ethyl alcohol, isopropyl alcohol, butyl
alcohol, acetone, methyl ethyl ketone, tetrahydrofuran, dimethyl
formamide and the like since otherwise gelation may sometimes take
place in the reaction product obtained by the reaction.
The molar ratio of the reactants, i.e. the amino-functional
organosilane compound or a hydrolysis product thereof and the
carboxylic acid anhydride, may usually be equimolar but the use of
an excessive amount of either one of the reactants over the other
to some extent has no particular disadvantages.
The other essential constituent in the component (B) than the above
described reaction product of the amino-functional organosilane
compound and the acid anhydride is a colloidal silica in the form
of an aqueous suspension, which is not limited to a product of a
specific type but preferably has a particle diameter in the range
from 10 to 40 nm stabilized with sodium or aluminum ions. Several
commercial products readily available on the market as such are
satisfactory for the purpose including Snowtex 40 sold by Nissan
Chemical Co. and the like.
The proportion of the reaction product of the amino-functional
organosilane compound and the acid anhydride and the colloidal
silica in the component (B) is such that from 0.1 to 20 parts by
weight or, preferably, from 0.5 to 5 parts by weight of the
reaction product are taken per 100 parts by weight of the colloidal
silica as solid. When the amount of the reaction product is smaller
than above, no sufficient improvement can be obtained in the
strength of adhesion of the cured rubbery material formed from the
emulsion composition by drying to the substrate on which the
composition is dried while an excessively large amount of the
reaction product may result in inferior flowability of the
composition.
The component (B) can be prepared by admixing the reaction product
of the amino-functional organosilane compound and the acid
anhydride dropwise into the colloidal silica in an aqueous
suspension kept at room temperature under agitation. In this
admixing procedure, certain amounts of insoluble matter may be
formed at the beginning stage but the whole mixture is uniformized
on further addition of the reaction product finally to give a
slightly turbid flowable mixture.
The amount of blending of this component (B) to the component (A)
is from 1 to 60 parts by weight or, preferably, from 3 to 30 parts
by weight of the component (B) as solid per 100 parts by weight of
the organopolysiloxane in the component (A). When the amount of the
component (B) is smaller than above, the rubbery elastomer obtained
by drying the emulsion composition may have poor mechanical
properties while an excessively large amount of the component (B)
results in decreased elongation of the cured rubbery elastomer
which may suffer cracking when the emulsion composition is used as
a coating material, especially, to give a coating layer of a
relatively large thickness.
It should be noted that the reaction product of the
amino-functional organosilane compound or a hydrolysis product
thereof and the acid anhydride in the component (B) serves not only
as an improver agent for the adhesion of the cured rubbery
elastomer obtained from the inventive emulsion composition to the
surface of the substrate but also to further increase the
reinforcing effect of the colloidal silica to the
organopolysiloxane in the component (A).
The component (C), which is a curing catalyst, is used to
accelerate curing of the rubbery elastomer when water is removed
from the inventive emulsion composition. Suitable curing catalysts
are exemplified by organotin compounds, i.e. compounds having at
least one tin-carbon linkage in a molecule, such as dibutyltin
dilaurate, dioctyltin dilaurate, dibutyltin diacetate and the like,
metal salts of carboxylic acids such as tin octoate, tin laurate,
iron octoate, lead octoate and the like and amine compounds such as
n-hexyl amine, guanidine and the like as well as hydrochlorides
thereof. It is a convenient way that the curing catalyst as above
named is emulsified in advance in water in a conventional manner by
use of an emulsifier to give an aqueous emulsion of oil-in-water
type, which is then admixed with the components (A) and (B). When
the curing catalyst is solid at room temperature, emulsification
thereof is facilitated by using a solution of the catalyst or by
carrying out the agitation at an elevated temperature higher than
the melting temperature of the catalyst.
The amount of this component (C) is not particularly limitative and
should be in a catalytic amount determined according to the desired
velocity of curing. The amount of the component (C) is usually in
the range from 0.01 to 10 parts by weight or, preferably, from 0.1
to 3 parts by weight per 100 parts by weight of the
organopolysiloxane in the component (A). When the amount is smaller
than 0.01 part by weight, the inventive composition after removal
of water cannot be fully cured even on prolonged standing while an
excessively large amount of the curing catalyst is rather
detrimental on the properties of the cured rubbery elastomer
obtained from the inventive composition with increased tendency
toward cracking but without further advantages.
In the preparation of the inventive composition by blending the
components (A), (B) and (C), it is essential that the component (B)
is prepared in advance separately from the component (A) by
uniformly mixing the colloidal silica in an aqueous suspension and
the reaction product of the amino-functional organosilane compound
and the acid anhydride. A preferable procedure for the preparation
of the inventive emulsion composition is that the aqueous emulsion
containing the organopolysiloxane as the component (A) is first
prepared which is then admixed successively with the component (B)
prepared separately and then with the component (C) under
agitation. The apparatus for the agitation of the mixture may be a
conventional mixing machine.
When the procedure for the preparation of the inventive emulsion
composition is not exactly as described above but a mixture
composed of the component (A), the colloidal silica and the
component (C) is first prepared to which the reaction product of
the amino-functional organosilane compound and the acid anhydride
is admixed, no satisfactory results can be obtained by the
formation of a gel-like material which cannot be solubilized to
give a uniform emulsion composition even under agitation of highest
intensity.
The aqueous emulsion composition of the invention should preferably
have a value of pH in the range from 5 to 9 or, more preferably,
from 6 to 9 in order to avoid any possible problems in the handling
of the composition or, in particular, on the safety of the workers
as well as to avoid corrosive attack thereof to the substrate
surface although the value of pH is not particularly limitative in
other respects. The value of pH of the composition may be
controlled by the addition of a suitable acid or alkali such as
acetic acid or sodium carbonate and the like depending on the value
of pH of the composition as prepared by blending the components (A)
to (C).
It is of course optional that the inventive aqueous emulsion
composition is admixed with various kinds of additives
conventionally formulated in aqueous coating compositions such as
thickeners, defoaming agents, pigments, dyes, preservatives,
penetrants and the like.
The above described aqueous emulsion composition of the invention
containing an organopolysiloxane is useful and widely applicable as
a coating composition, fiber treating agent, mold release agent,
back-surface releaser of adhesive tapes, binder for inorganic
materials and the like.
Following are the examples of the present invention and comparative
examples, in which parts are all given by parts by weight.
EXAMPLE 1
Three aqueous emulsions as the component (A) each containing an
organopolysiloxane and having a different value of pH were prepared
by emulsifying 500 parts of octamethylcyclotetrasiloxane, 25 parts
of methyl trimethoxy silane and 10 parts of dodecyl benzene
sulfonic acid in 465 parts of water followed by passing the
emulsion twice through a homogenizer under a pressure of 3000
p.s.i. to stabilize the emulsion and heating the thus stabilized
aqueous emulsion in a flask at 70.degree. C. for 12 hours with
subsequent cooling to room temperature and controlling the value of
pH to 5.0, 8.0 and 12.0, respectively, by the addition of sodium
carbonate after 24 hours of standing. These aqueous emulsions are
referred to hereinafter as A-1, A-2 and A-3 for the values of pH of
5.0, 8.0 and 12.0, respectively.
The content of non-volatile matter in each of these aqueous
emulsions was 47% by weight and the organopolysiloxane contained in
the emulsion and separated therefrom by use of methyl alcohol had a
viscosity of 7200 centipoise as a 20% by weight solution in toluene
at 25.degree. C.
Separately from the above, 221 parts of 3-aminopropyl
triethoxysilane were added dropwise at room temperature into a
mixture of 98 parts of maleic acid anhydride and 319 parts of ethyl
alcohol under agitation to give a reaction product of the silane
and the acid anhydride. Into 1000 parts of a colloidal silica at a
pH of 9.3 containing 40 % by weight of the solid content and 0.6%
by weight of Na.sub.2 O (Snowtex 40, a product by Nissan Chemical
Co.) were added dropwise 30 parts of the above prepared alcohol
solution of the reaction product at room temperature under
agitation to give a somewhat cloudy product having a pH of 3.4,
which was used as the component (B-1).
Further, a component (C) was prepared by emulsifying 30 parts of
dibutyltin dilaurate and 1 part of polyoxyethylene nonyl phenyl
ether in 69 parts of water in a conventional procedure.
The above prepared components (A), (B) and (C) were blended
together in a proportion indicated in Table 1 to give Compositions
No. 1 to No. 9 below and each of the thus prepared compositions was
cast on a plate of a fluorocarbon resin and kept as such at
25.degree. C. for 48 hours in an atmosphere of 60% relative
humidity to be dried into a cured rubbery sheet of about 1 mm
thickness.
This rubbery sheet was tested for the hardness, tensile strength
and ultimate elongation at break according to the procedures
specified in JIS K 6301 to give the results shown in Table 1, which
also includes the formulations of the components calculated as
solid and the results of testing for the comparative compositions
No. 10 and No. 11 prepared by omitting the component (B) and by
adding instead 15 parts as solid of Snowtex 40 alone (No. 10) or 15
parts of a 97:3 by weight mixture of Snowtex 40 (calculated as
solid) and 3-aminopropyl triethoxysilane (No. 11).
Each of the above prepared aqueous emulsion compositions was spread
on various kinds of substrate materials including concrete, cement
mortar, glass, wood, steel, paper board and asbestos board and
dried and cured on the substrate in the same manner as above and
the adhesion of the cured rubbery sheet and the substrate surface
was examined. The adhesion was complete in each of the cured
rubbery layers obtained from the composition according to the
invention in which separation of the rubber sheet and the substrate
did not take place but the rubbery sheet per se was destroyed when
the rubbery sheet was forcibly pulled off the substrate at a
velocity of about 300 mm/minute in the vertical direction except
for the substrates of the steel plate and paper board where
separation could take place at the interface though with a
considerably large pulling force. On the contrary, the adhesion of
the cured rubber layers obtained from the above prepared
comparative compositions No. 10 and No. 11 to the substrate surface
was not always complete. The results of this adhesion test with
these comparative compositions are shown in Table 2 below, in which
the symbols A, B and C each indicate the following condition of
adhesion.
TABLE 1 ______________________________________ Com- Properties of
cured rubber posi- Components, PH of Hard- Tensile Ultimate tion
parts compo- ness strength, elonga- No. A B C sition (JIS)
kg/cm.sup.2 tion, % ______________________________________ 1 A-1
B-1 1.5 4.3 14 15 980 100 7.5 2 A-1 B-1 1.5 3.9 20 20 900 100 15 3
A-1 B-1 1.5 3.7 35 25 850 100 30 4 A-2 B-1 1.5 7.2 15 17 950 100
7.5 5 A-2 B-1 1.5 6.5 22 22 880 100 15 6 A-2 B-1 1.5 6.0 35 27 830
100 30 7 A-3 B-1 1.5 11.0 15 17 970 100 7.5 8 A-3 B-1 1.5 10.2 20
21 860 100 15 9 A-3 B-1 1.5 9.4 34 25 830 100 30 10 A-2 * 1.5 9.5
20 15 600 100 11 A-2 * 1.5 11.0 20 16 650 100 12 A-1 B-2 1.5 4.5 15
15 980 100 7.5 13 A-1 B-2 1.5 4.2 20 20 900 100 15 14 A-1 B-2 1.5
4.0 35 25 850 100 30 15 A-2 B-2 1.5 7.6 15 16 960 100 7.5 16 A-2
B-2 1.5 6.8 21 22 870 100 15 17 A-2 B-2 1.5 6.5 35 27 840 100 30 18
A-3 B-2 1.5 11.3 15 16 980 100 7.5 19 A-3 B-2 1.5 10.8 20 22 890
100 15 20 A-3 B-2 1.5 9.6 35 26 870 100 30
______________________________________ *See text.
TABLE 2 ______________________________________ Composition No.
Substrate 10 11 ______________________________________ Concrete C A
Cement mortar C A Glass plate B B Wood board C B Steel plate C B
Paper board B B Asbestos board C A
______________________________________
Each of the above prepared emulsion compositions was further
subjected to curing by drying at room temperature to form a cured
rubber layer of 5 mm thickness to find that the cured rubber layers
formed from the inventive compositions No. 1 to No. 9 were free
from any cracks while those formed from the comparative
compositions No. 10 and No. 11 had cracks.
Further, storage test was undertaken with the above prepared
emulsion compositions, each of which was kept standing at
25.degree. C. for 3 months. No changes were noted with the
inventive compositions No. 1 to No. 9 in the appearance of the
emulsion, curing behavior, mechanical properties of the cured
rubber sheets and adhesion of the cured rubber layers to the
surface of various substrates. The comparative compositions No. 10
and No. 11 were also stable in this storage test.
* * * * *